Dosimetry and radiation dose distribution in tumors for radioimmunotherapy: The effect of tumor size

For aiding to optimize the efficiency of radioimmunotherapy with β-emitter-labeled monoclonal antibody (MAb), radiation absorbed dose in a small tumor was calculated using a mathematical model for ⁶⁷Cu, ⁹⁰Y, ¹³¹I, ¹⁸⁶Re, and ¹⁸⁸Re. MAb distributions were assumed to be uniform or exponential to investigate the tumor size effect on absorbed dose. The salient results are 1) with longer range β-emitters, radiation absorbed dose is increased with the tumor size increases and the fraction of radiation dose to the outside of the tumor is large; 2) with shorter range β-emitters, the tumor size effect on absorbed dose is small. The fraction of radiation dose to the tumor is large and small tumors will be irradiated effectively; 3) when MAb distribution is non-uniform, absorbed dose is more homogenous with longer range β-emitters.